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Hello,

I just created an Electrum multisig in Tails (totally offline), and one of the signatures must come from a Trezor one. When I try to sign, there's a message: "missing previous tx".

Can someone help me about this error?

I was using Electrum 4.0.9 and now tried 4.3.4. Same problem. All the process was done totally offline, I don't want to go online to sign anything.

I try to sign with the Trezor first, or last, or in the middle. Same problem. All the signatures go well except the Trezor's.

The wallet created just has master keys for the other signatures, except for the Trezor's.

Thank you.

I've not come across this error before. Here is the code from the Trezor plugin for Electrum which is throwing this error: https://github.com/spesmilo/electrum/blob/4aa319e5c31543883346e28a5459fa3642601be6/electrum/plugins/trezor/trezor.py#L84

As it says, it can't find the UTXO for the input you are trying to spend. How have you created this transaction you are trying to sign? Are you sure it is a valid transaction?

Secondly, make sure the Trezor is up to date, and also ensure that you have the correct wallet open on the Trezor. Did you use a passphrase when setting up the wallet and have forgotten to enter it this time?

There have been a number of problems in the past with Trezor devices and multi-sig in the past, so this might be nothing you are doing wrong but rather a problem with Trezor.

Thanks for the answer.

I've created the transation in the Electrum app in my smartphone. It's a watch only wallet since it has all the cosigners master keys only. So I can create the transaction and sign using my offline devices.

The transaction is valid, and it works when I sign with other cosigners other than Trezor.

I recently updated the firmware and installed that one exclusive for bitcoin. Maybe this is the problem. I will try to change and answer here.

The passphrase is correct. When it is not, the Electrum show an error message. And the addresses are correct, and the sign button is there. I tried to do it again many times. Same error.

I try to run Electrum with Trezor - not multisig. Create an account, received btc, and when I try to send them using the same procedure, from my watch only account in my cellphone and sign in Electrum, surprise, same error: missing previous tx.

Is it SegWit? Try to use Electrum v4.3.2 if the issue will persist.

If not, it may have something to do with this Commit: https://github.com/spesmilo/electrum/commit/d3227d7489fe327bd40e891a517c86bd207227ec (https://github.com/spesmilo/electrum/commit/d3227d7489fe327bd40e891a517c86bd207227ec) (in v4.3.3)

If still there, enable logging and check if it has something that's related to the error.
You can enable logging in "Tools->Preferences->Misc->Write logs to file" (restart Electrum), reproduce the error and then disable logging.
Log is in "logs" folder inside Electrum's datadir (location (https://electrum.readthedocs.io/en/latest/faq.html#where-is-the-electrum-datadir-located)).

Yes, it is segwit. I will try all these steps and get back to you here.

Thank you very much.

It won't learn about utxos until you go online so i'm guessing that's what you need to do. Take the electrum wallet paired with trezor online.

Was v4.0.9 had the same error? Because I might have misunderstood that part in the OP.
If so, the commit that I linked might not be the cause of issue.

4.0.9 was the first one I've tested. Also 4.3.4 and 4.3.2. Always the same problem.

I couldn't find the log file in Tails. Where is it?

I really didn't want to go online, it will compromisse my passphrase. Maybe if I use a virtual keyboard, what do you think?

Thanks for your help. I really apreciate it.

I went online and it worked. I used Tails, without persistent, I guess it would not compromisse my passphrase.

Thanks for all the help here, guys. If you have more ideas, they will be welcome  ;D

The wallet file and electrum data directory which will be stored in the persistent drive will not contain any data that'll compromise your Trezor.
In worst case scenario, an attacker can only get access to your transaction history.

OP has made it by taking your suggestion. Kudos. But why it has to be online to make it work?

If there is no connection to the internet, it's not possible for electrum to get synced to the blockchain and it wouldn't have any information about the transactions already made.
Take note that even if you want to make a transaction offline in electrum, you need an online device too. The online device is required for getting UTXOs data and broadcasting your tranaction.

The transaction is created in a watch-only wallet, which is online.

But all the signatures are made by offline devices. So I want to connect the trezor to a computer and sign it, offline.

Thanks.

yes, OP's doing quite decent. It should have worked. I did the same excepting using a trezor as a co-signer and it worked. Looks like the problem is the trezor itself.

I don't think that this is considered as off-topic but has anyone tried to follow this[1] guide to access Trezor Web Wallet within Tails OS? Does it even make sense to access the wallet by using the previous procedure or should we just create a new wallet in Electrum (within Tails OS) using the usual procedure for hardware wallets? It seems that the previous method even has an open issue[2] that makes the web interface unable to connect due to being blocked by Ferm...

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[1]https://mcudev.github.io/tails-web-wallet.html (https://mcudev.github.io/tails-web-wallet.html)